Access to plumbing fixtures in a false ceiling

 The plumbing fixtures for our second level bathroom are located in a false ceiling of the bathroom in the unit below. When the bathrooms were built about 35 years ago each bathroom ceiling consisted of removable panels to allow access to fix any problems such as blockages in the unit above it.

  A blockage has occurred in our bathroom waste pipe and our plumber says he can fix it by accessing the pipes below.

  However on inspection, he found that the access panels had been replaced with a permanent expensive cedar panelled ceiling. He advised the owner that he could access the pipes by installing a cheap cedar snap vent about 12 cm square. The owner rejects this and is insisting on a full ceiling replacement costing about $1400 as a condition of permitting access to his unit.

I would appreciate advice on the following :   1. In the absence of a special resolution to change their ceiling without permission, who owns the ceiling?

2. As the OC must maintain the common property pipes, is it their responsibility to pay for the expensive option of replacing the whole (illegal?) ceiling to fix the plumbing or can they insist on the cheaper option of a $20 snap vent?

 To complicate matters, the blockage was caused by our recent bathroom renovation and the company responsible is willing to pay to fix the problem but is  understandably reluctant to pay for the dearer option, especially as the owner will not consider any other options to access the ceiling such as removal and replacement of just one or two cedar panels. As the owners we are left to negotiate the tricky strata issues!